The notion that underwire bras give you breast cancer popped
up in the ‘90s, and thankfully, it’s just a myth. The idea was that underwire
trapped toxins in the breast tissue, which could cause cancer, according to Scientific American.

Thankfully, that theory has never been supported by any
research. Doctors point to the fact that it’s easier to demonize innocent
things like bras instead of focusing on the more likely factors, such as
hormones.